Basics of Number System for Competitive Exams. Number system is the way of writing numbers. Numerals or symbols are represented as a number depending upon the number system. Binary, Octal, Decimal, Hexadecimal, etc. are some popular number systems.

### Decimal Number System

Decimal number system is the most commonly used and also called the Hindu-Arabic number system.

There are total ten digits (0to 9) used in the decimal number system. So it is a base 10 number system.

Two types of values of a digit in a number:**(1) Face Value** – Face Value is the value of the digit itself.**(2) Place Value** – Place value depends upon the position of the digit in the number.

Every place in a number is 10 times more to the immediate right place.

#### Representation of a Number

**(1) Standard Form**:

Example: 1234.5678**(2) Expanded Form**:

Example: 1000+200+30+4+0.5+0.06+0.007+0.0008**(3) Word Form**

Example: One thousand two hundred thirty four and (point) five thousand six hundred seventy eight ten thousandth